1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package kademlia
import (
"fmt"
"math/rand"
"strings"
"github.com/ethereum/go-ethereum/common"
)
type Address common.Hash
func (a Address) String() string {
return fmt.Sprintf("%x", a[:])
}
func (a *Address) MarshalJSON() (out []byte, err error) {
return []byte(`"` + a.String() + `"`), nil
}
func (a *Address) UnmarshalJSON(value []byte) error {
*a = Address(common.HexToHash(string(value[1 : len(value)-1])))
return nil
}
// the string form of the binary representation of an address (only first 8 bits)
func (a Address) Bin() string {
var bs []string
for _, b := range a[:] {
bs = append(bs, fmt.Sprintf("%08b", b))
}
return strings.Join(bs, "")
}
/*
Proximity(x, y) returns the proximity order of the MSB distance between x and y
The distance metric MSB(x, y) of two equal length byte sequences x an y is the
value of the binary integer cast of the x^y, ie., x and y bitwise xor-ed.
the binary cast is big endian: most significant bit first (=MSB).
Proximity(x, y) is a discrete logarithmic scaling of the MSB distance.
It is defined as the reverse rank of the integer part of the base 2
logarithm of the distance.
It is calculated by counting the number of common leading zeros in the (MSB)
binary representation of the x^y.
(0 farthest, 255 closest, 256 self)
*/
func proximity(one, other Address) (ret int) {
for i := 0; i < len(one); i++ {
oxo := one[i] ^ other[i]
for j := 0; j < 8; j++ {
if (uint8(oxo)>>uint8(7-j))&0x01 != 0 {
return i*8 + j
}
}
}
return len(one) * 8
}
// Address.ProxCmp compares the distances a->target and b->target.
// Returns -1 if a is closer to target, 1 if b is closer to target
// and 0 if they are equal.
func (target Address) ProxCmp(a, b Address) int {
for i := range target {
da := a[i] ^ target[i]
db := b[i] ^ target[i]
if da > db {
return 1
} else if da < db {
return -1
}
}
return 0
}
// randomAddressAt(address, prox) generates a random address
// at proximity order prox relative to address
// if prox is negative a random address is generated
func RandomAddressAt(self Address, prox int) (addr Address) {
addr = self
var pos int
if prox >= 0 {
pos = prox / 8
trans := prox % 8
transbytea := byte(0)
for j := 0; j <= trans; j++ {
transbytea |= 1 << uint8(7-j)
}
flipbyte := byte(1 << uint8(7-trans))
transbyteb := transbytea ^ byte(255)
randbyte := byte(rand.Intn(255))
addr[pos] = ((addr[pos] & transbytea) ^ flipbyte) | randbyte&transbyteb
}
for i := pos + 1; i < len(addr); i++ {
addr[i] = byte(rand.Intn(255))
}
return
}
// KeyRange(a0, a1, proxLimit) returns the address inclusive address
// range that contain addresses closer to one than other
func KeyRange(one, other Address, proxLimit int) (start, stop Address) {
prox := proximity(one, other)
if prox >= proxLimit {
prox = proxLimit
}
start = CommonBitsAddrByte(one, other, byte(0x00), prox)
stop = CommonBitsAddrByte(one, other, byte(0xff), prox)
return
}
func CommonBitsAddrF(self, other Address, f func() byte, p int) (addr Address) {
prox := proximity(self, other)
var pos int
if p <= prox {
prox = p
}
pos = prox / 8
addr = self
trans := byte(prox % 8)
var transbytea byte
if p > prox {
transbytea = byte(0x7f)
} else {
transbytea = byte(0xff)
}
transbytea >>= trans
transbyteb := transbytea ^ byte(0xff)
addrpos := addr[pos]
addrpos &= transbyteb
if p > prox {
addrpos ^= byte(0x80 >> trans)
}
addrpos |= transbytea & f()
addr[pos] = addrpos
for i := pos + 1; i < len(addr); i++ {
addr[i] = f()
}
return
}
func CommonBitsAddr(self, other Address, prox int) (addr Address) {
return CommonBitsAddrF(self, other, func() byte { return byte(rand.Intn(255)) }, prox)
}
func CommonBitsAddrByte(self, other Address, b byte, prox int) (addr Address) {
return CommonBitsAddrF(self, other, func() byte { return b }, prox)
}
// randomAddressAt() generates a random address
func RandomAddress() Address {
return RandomAddressAt(Address{}, -1)
}
|
